The prior art has developed according to the references cited in U.S. Pat. No. 3,802,724 issued Apr. 9, 1974 and assigned to the assignee of this application.
Prior art techniques, for the most part, have been based upon the utilization of competing chemical formulations which are or may be employed as either an overlay on the top surface of the document to be protected or as an overprinted area on such documents or in some instances as a chemical wash or bath into which the entire paper stock is emersed and from which the document is thereafter preprinted. None of the known techniques has direct application to computerized document protection nor are any of the known prior art systems readily adapted to document protection of computer printouts as hereinafter described.
Improvements of U.S. Pat. No. 3,802,724 related to a combined document using a document protection system for use with high speed data processing equipment such, for example, as high speed printers, which produce visibly legible records from a computer, the document being safeguarded by a pattern of legible warning data camouflaged by a pattern applied to a film covering of the warning date so that if the covering is altered, the warning data will appear.
Since the general quality of printing by such high speed computer printouts is usually fairly poor, it is a relatively easy matter for the document forger or check alterer to raise, change or remove and add the amount and/or signature at will. The same is generally true for the average typewritten document, check, etc. The printing on these materials is generally so inferior that alteration by hand of the amount or signature is accomplished with ease and efficiency by the individual.
The system contemplated in U.S. Pat. No. 3,802,724 employs a high tensile strength, transparent material which is pre-cut in the form of a tape which is or may be produced in a relatively large roll. The transparent material is required to have a friction coefficient sufficient to avoid marking by known means such, for example, as ball point pens, crayons, wax pencils, and the like. The tape is provided with a lightly colored camouflage pattern on one surface which is overcoated with a highly aggressive, pressure-sensitive, adhesive coating. The opposite surface of the transparent tape is coated with a curable colorless silicone resin. The document to which the pressure sensitized tape is to be applied is or may be provided with a lightly colored, so-called VOID pattern of repeating symbology such, for example, as the word "void", "fraud", "cancelled" or some similar designation. Thereafter the tape with the camouflage protective coating is adhesively secured over the area containing the void pattern, thus masking the "void" pattern from the eye while permitting any more darkly colored, printed indicia such, for example, as the number amount in the case of a check or the signature of the payer of the document to be visibly discernable through the tape. The document thus protected cannot be written upon in a protected area with the generally available writing instruments due to the slipperiness of the exposed surface provided by the invention. Attempts at complete or partial removal of the applied tape result in damage to the document, e.g. tearing, mutilitation, holes in the protected area, etc.
Since the advent of quality color xerographic copiers, such as the Xerox L-6500 color copier, copies of documents have posed an ever increasing problem.
The very effective system disclosed in U.S. Pat. No. 3,802,724 can be thwarted by making a color copy of the original and then altering the amount.
In addition, because the systems of color copying are so effective, criminals having access to them may effectively duplicate negotiable bonds, vehicle registrations and title to match them to the stolen vehicle, personal identification documents, and other like documents. As the copier systems proliferate, so does their usage and the opportunity to make nefarious copies.